Patent Application
20070089990
1. Field of the Invention
Embodiments of the present invention generally relate to semiconductor processing. More specifically, embodiments of the present invention generally relate to a control scheme for electroplating solutions.
2. Description of the Related Art
Electroless and electroplating deposition techniques have become an attractive option for depositing copper and copper alloys onto semiconductor substrates and into high aspect ratio features.
Conventional electroplating methods generally include positioning a substrate into an electrolytic solution. An electrical bias is then applied between the surface of the substrate and an anode positioned in the electrolytic solution which operates to urge copper ions to deposit on the substrate surface. During non-processing time periods, i.e., when substrates are not being plated, the electrolytic solution is generally circulated through a continual fluid path that includes a relatively small volume plating region and a substantially larger volume storage region. The storage region, for example, may hold approximately 15 liters of the electrolytic solution, while the plating region may hold approximately 2 liters of the electrolytic solution. Additionally, the continual fluid path may include an electrolyte replenishment device configured to replenish portions of the electrolytic solution that may be depleted through plating operations.
Typical electrolyte solutions used for copper electroplating generally consist of copper sulfate solution having sulfuric acid and copper chloride added thereto. The sulfuric acid generally operates to modify the acidity and conductivity of the solution, while the copper chloride provides negative chlorine ions needed for nucleation of suppressor molecules and facilitates proper anode corrosion. The electrolytic solutions also generally contain various organic molecules which may be accelerators, suppressors, levelers, brighteners, etc. These organic molecules are generally added to the electrolytic solution in order to facilitate void-free fill of features and planar copper deposition. Accelerators may be sulfide-based molecules that locally accelerate electrical current at a given voltage where they absorb. Suppressors may be polymers of polyethylene glycol, mixtures of ethylene oxides and propylene oxides, or block copolymers of ethylene oxides and propylene oxides which tend to reduce electrical current at the sites where they absorb and slow plating at those locations. Levelers may be nitrogen containing long chain polymers which operate to facilitate planar copper deposition.
During the plating process, copper ions are continually being removed from and replenished to the electrolytic solution. Thus, the copper concentration of the electrolytic solution may change or vary over time. This concentration change may further be affected by volume depletion of the electrolytic solution or dissolution of the anode. The volume of water within the electrolytic solution is also in flux as the electrolytic solution is consumed, evaporates, and is retained by the supply piping, volume storage region, or the plating region.
Additionally, plating operations deplete the various organic molecules in the electrolyte solution and each organic concentration also varies over time. For example, levelers are known to deplete and breakdown upon exposure to oxygen containing elements such as ambient air, oxygen absorbed into the electrolytic solution, oxygen molecules contained in the anode metal, or oxidation encountered during plating by incorporation into a growing film. This breakdown process generates free radicals in the electrolytic solution, which are undesirable because the free radicals can deposit on a substrate and contaminate the metal layer. Further, levelers are known to break down upon exposure to copper, copper alloys, and platinum, all of which are typical anode materials for electroplating systems. Similarly, accelerators and suppressors may also suffer from depletion and breakdown characteristics as a result of oxygen or metal exposure.
Depletion of organics is not limited to processing time periods because the electrolyte solution in an electroplating system is generally continually circulated through the plating region and the volume storage region during non-processing time periods. As a result of the circulation, the electrolyte solution may be continually exposed to both oxygen-containing elements and the metal anode. Thus, the organic molecules in the electrolyte solution are continually being depleted, even though the plating region is not in a plating or operational mode.
Because the concentration of the organics in the electrolyte solution and the concentration of the radicals generated by the organic molecule degradation and depletion have a substantial effect upon the efficiency and controllability of plating operations, replenishment of depleted organics in the electrolyte solution to maintain specific organic concentrations is desired. Conventional plating systems generally provide a replenishment module configured to add fresh organics into the electrolyte solution in order to replenish depleted organic molecules. However, conventional organic replenishment processes generally require time consuming organic molecule measurement processes, which decrease the accuracy of conventional organic replenishment processes. This variance in organic concentration may detrimentally affect the ability to accurately control conventional electroplating apparatus. Therefore, there exists a need for a method for accurately replenishing organic molecules and water in an electroplating bath during plating operations.
The present invention generally provides method and apparatus for dosing an electrolyte solution including measuring the time after adding fresh solution, measuring the total Amp-hours used during electroplating after adding fresh solution, measuring the number of substrates processed after adding fresh solution, calculating the volume of a dose to supply to the electrolyte solution based on the time, the total Amp-hours, and the number of substrates processed, and adding the dose to the electrolyte solution.
The present invention also generally provides method and apparatus for supplying a dose to an electrolyte solution including measuring the loss of a volume of fluid from a solution vessel, measuring the time after adding fresh solution, measuring the total Amp-hours used during electroplating after adding fresh solution, measuring the number of substrates processed by the electrolyte solution, calculating a dose to supply to the electrolyte solution based on the time, the total Amp-hours, and the number of substrates processed, and adding the dose to the electrolyte solution.
The present invention also generally provides method and apparatus for dosing an electroplating bath including monitoring total Amp-hours used during electroplating, monitoring total evaporation loss during electroplating, dosing water and chemicals to the electroplating bath after either the total Amp-hours or the total evaporation loss exceed set targets, and then resetting both the total Amp-hours and the total evaporation loss to zero.
So that the manner in which the above recited features of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments.
The present invention provides a control system for delivering electrolyte solution to electroplating baths. The control system uses time, amp-hours, and number of substrates processed to supply a dose of chemicals to the electrolyte solution delivery system. Embodiments of the invention generally provide an electrochemical plating system configured to plate conductive materials, such as metals, on a semiconductor substrate for use in apparatus implementing multiple chemistries or a single chemical profile on a single plating platform. Embodiments of the invention may be used for measuring, adding, or mixing chemical components for various plating processes, including, but not limited to direct plating on a barrier layer, alloy plating, alloy plating combined with convention metal plating, plating on a thin seed layer, optimized feature fill and bulk fill plating, plating multiple layers with minimal defects, or any other plating process where more than one chemistry may be beneficial to a plating process.
While the following description of the volume measurement device is directed to use in an electrochemical processing system (ECP), such as the SLIMCELL™ system available from Applied Materials, Inc. of Santa Clara, Calif., the invention contemplates the use of the invention where precise chemical composition of liquids may be added to form processing composition. For example, embodiments may be used in combination with chemical mechanical polishing apparatus, such as the MIRRA® MESA™ polishing system and the REFLEXION™ processing system, commercially available from Applied Materials, Inc., of Santa Clara, Calif., wet clean process apparatus, such as the TEMPEST™ wet clean apparatus available from Applied Materials, Inc., of Santa Clara, Calif. and other liquid processing systems.
ECP system 100 further includes a factory interface (FI) 130. FI 130 includes at least one FI robot 132 positioned adjacent a side of the FI 130 that is adjacent the processing base 113. This position of robot 132 allows the robot to access substrate cassettes 134 to retrieve a substrate 126 and then deliver the substrate 126 to one of several processing locations 114, 116 to initiate a processing sequence. Similarly, robot 132 may be used to retrieve substrates from one of the processing locations 114, 116 after a substrate processing sequence is complete. In this situation, robot 132 may deliver the substrate 126 to one of the cassettes 134 for removal from the system 100. Additionally, robot 132 is configured to access an anneal chamber 135 positioned in communication with FI 130. The anneal chamber 135 generally includes a two position annealing chamber, wherein a cooling plate or position 136 and a heating plate or position 137 are positioned adjacently with a substrate transfer robot 140 positioned between the two stations. The robot 140 is generally configured to move substrates between the respective heating 137 and cooling plates 136.
Generally, process locations 102, 104, 106, 108, 110, 112, 114, 116 may be any number of processing cells for use in an electrochemical plating platform. Plating solution delivery systems 111A, 111B and a controller 115 deliver electrolyte solution to the process locations. More particularly, the process locations may be configured as electrochemical plating cells, rinsing cells, bevel clean cells, spin rinse dry cells, substrate surface cleaning cells, electroless plating cells, metrology inspection stations, and other cells or processes that may be beneficially used in conjunction with a plating platform.
Returning to
The head assembly 211 is mounted to a head assembly frame 252. The head assembly frame 252 includes a mounting post 254 and a cantilever arm 256. The mounting post 254 is coupled to the base 160 and the cantilever arm 256 extends laterally from an upper portion of the mounting post 254 and rotates about a vertical axis of the mounting post 254 to allow movement of the head assembly 211 over or clear of the basins 240, 272. The head assembly 211 is attached to a mounting plate 260 disposed at the distal end of the cantilever arm 256. The lower end of the cantilever arm 256 is connected to a cantilever arm actuator 268, such as a pneumatic cylinder, mounted on the mounting post 254. The cantilever arm actuator 268 provides pivotal movement of the cantilever arm 256 with respect to the mounting post 254. When the cantilever arm actuator 268 is retracted, the cantilever arm 256 moves the head assembly 211 away from the anode assembly 220 disposed in the inner basin 272 to provide the spacing required to remove and/or replace the anode assembly 220 from the first process cell 150. When the cantilever arm actuator 268 is extended, the cantilever arm 256 moves the head assembly 211 axially toward the anode assembly 220 to position the substrate in the head assembly 211 in a processing position. The head assembly 211 may also tilt to orientate a substrate at an angle from horizontal.
The head assembly 211 includes a substrate holder assembly 250 and a substrate assembly actuator 258. The substrate assembly actuator 258 is mounted onto the mounting plate 260 and includes a head assembly shaft 262 that extends downward through the mounting plate 260. The lower end of the head assembly shaft 262 is connected to the substrate holder assembly 250 to position the substrate holder assembly 250 in a processing position and in a substrate loading position. The substrate assembly actuator 258 additionally may be configured to provide rotary motion to the head assembly 211. In one embodiment, the head assembly 211 is rotated between about 2 rpm and about 50 rpm during an electroplating process and often may be rotated between about 5 and about 20 rpm. The head assembly 211 can also be rotated as the head assembly 211 is lowered to position the substrate in contact with the plating solution in the process cell as well as when the head assembly 211 is raised to remove the substrate from the plating solution in the process cell. The head assembly 211 may be rotated at a high speed such as greater than 20 rpm after the head assembly 211 is lifted from the process cell to enhance removal of residual plating solution from the head assembly 211 and substrate.
The substrate holder assembly 250 includes a thrust plate 264 and a cathode contact ring 266. The cathode contact ring 266 is configured to electrically contact the surface of the substrate to be plated. Typically, the substrate has a seed layer of metal, such as copper, deposited on the feature side of the substrate. A power source 246 is coupled between the cathode contact ring 266 and the anode assembly 220 and provides an electrical bias that drives the plating process.
The thrust plate 264 and the cathode contact ring 266 are suspended from a hanger plate 236. The hanger plate 236 is coupled to the head assembly shaft 262. The cathode contact ring 266 is coupled to the hanger plate 236 by hanger pins 238. The hanger pins 238 allows the cathode contact ring 266, when mated against the inner basin 272, to move to closer to the hanger plate 236. This allows the substrate held by the thrust plate 264 to be sandwiched between the hanger plate 236 and thrust plate 264 during processing, thereby ensuring good electrical contact between the seed layer of the substrate and the cathode contact ring 266.
The anode assembly 220 is positioned within a lower portion of the inner basin 272 below the substrate holder assembly 250. The anode assembly 220 includes one or more anodes 244 and a diffusion plate 222. The anode 244 is disposed in the lower end of the inner basin 272 and the diffusion plate 222 is disposed between the anode 244 and the substrate held by the substrate holder assembly 250 at the top of the inner basin 272. The anode 244 and diffusion plate 222 are maintained in a spaced-apart relation by insulative spacer 224. The diffusion plate 222 is attached to and substantially spans the inner opening of the inner basin 272. The diffusion plate 222 is permeable to the plating solution and is fabricated from a plastic or ceramic material, for example, an olefin such as a spunbonded polyester film. The diffusion plate 222 operates as a fluid flow restrictor to improve flow uniformity across the surface of the substrate. The diffusion plate 222 also operates to damp electrical variations in the electrochemical cell to control electrical flux which improves plating uniformity. Alternatively, the diffusion plate 222 may be fabricated from a hydrophilic plastic, such as treated PE, PVDF, PP, or other porous or permeable material that provides electrically resistive damping characteristics.
The anode assembly 220 may include a consumable anode 244 to serve as a metal source. Alternatively, the anode 244 may be a non-consumable anode, and the metal to be electroplated is supplied within the plating solution from the plating solution delivery system 111. The anode assembly 220 may be a self-enclosed module having a porous enclosure preferably made of the same metal as the metal to be electroplated, such as copper. Alternatively, the enclosure may be fabricated from porous materials, such as ceramics or polymeric membranes. Exemplary consumable and non-consumable anodes include copper/doped copper and platinum, respectively. The anode 244 is metal particles, wires, a perforated sheet, or a combination and is manufactured from the material to be deposited on the substrate, such as copper, aluminum, gold, silver, platinum, tungsten, copper phosphate, noble metal, or other materials which may be electrochemically deposited on a substrate. The anode 244 may be porous, perforated, permeable, or otherwise configured to allow passage of the plating solution. Alternatively, the anode 244 may be solid. Compared to a non-consumable anode, the consumable (i.e., soluble) anode provides gas-generation-free plating solution and minimizes the need to constantly replenish the metal in the plating solution. In the embodiment depicted in
An electrolyte inlet 216 is formed through the inner basin 272. The plating solution entering the inner basin 272 through the electrolyte inlet 216 flows through or around the anode assembly 220 upward toward the surface of the substrate positioned on the upper end of the inner basin 272. The plating solution flows across the substrate surface and through slots (not shown) in the cathode contact ring 266 to a passage formed in the outer basin 240. The bias between the substrate and the anode 244 causes metal ions from the plating fluids and/or anode to deposit on the surface of the substrate. Examples of process cells that may be adapted to benefit from the invention are described in U.S. patent application Ser. No. 09/905,513, filed Jul. 13, 2001, and in U.S. patent application Ser. No. 10/061,126, filed Jan. 30, 2002, both of which incorporated by reference.
In another embodiment, a first plating solution and a separate and different second plating solution can be provided sequentially to a single plating cell. Typically, providing two separate chemistries to a single plating cell requires the plating cell to be drained and/or purged between the respective chemistries; however, a mixed ratio of less than about 10 percent first plating solution to the second plating solution should not be detrimental to film properties.
More particularly, the plating solution delivery system 111A, 111B typically includes a plurality of chemical component sources 302 and at least one electrolyte source 304 that are fluidly coupled to each of the processing cells of system 100 via a valve manifold 332. Typically, the chemical component sources 302 include an accelerator source 306, a leveler source 308, and a suppressor source 310. The accelerator source 306 is adapted to provide an accelerator material that typically adsorbs on the surface of the substrate and locally accelerates the electrical current at a given voltage where they adsorb. Examples of accelerators include sulfide-based molecules. The leveler source 308 is adapted to provide a leveler material that operates to facilitate planar plating. Examples of levelers are nitrogen containing long chain polymers. The suppressor source 310 is adapted to provide suppressor materials that tend to reduce electrical current at the sites where they adsorb (typically the upper edges/corners of high aspect ratio features). Therefore, suppressors slow the plating process at those locations, reducing premature closure of the feature before the feature is completely filled and minimizing detrimental void formation. Examples of suppressors include polymers of polyethylene glycol, mixtures of ethylene oxides and propylene oxides, or copolymers of ethylene oxides and propylene oxides.
In order to prevent situations where a chemical component source runs out and to minimize chemical component waste during containers replacement, each of the chemical component sources 302 generally includes a bulk or larger storage container coupled to a smaller buffer container 316. The buffer container 316 is generally filled from the containers 306, 308, and 310, and therefore, the containers 306, 308, and 310, may be removed for replacement without affecting the operation of the fluid delivery system, as the associated buffer container may supply the particular chemical component to the system while the containers are being replaced. The volume of the buffer container 316 is less than the volume of the containers 306, 308, and 310. The containers 306, 308, and 310 are sized to contain enough chemical components for 10 to 12 hours of uninterrupted operation. This provides sufficient time for operators to replace the containers when the containers are empty. If the buffer container was not present and uninterrupted operation was still desired, the containers would have to be replaced prior to being empty, thus resulting in significant chemical component waste.
In the embodiment depicted in
A first liquid inlet port 315 is coupled to a chemical component dosing pump 311 disposed between the volume measurement module 312 and the chemical component sources 306, 308, and 310. The chemical component dosing pump 311 provides the chemical components to the module 312 via the pump line 319 and may also be adapted to provide additional liquids, such as electrolyte 304, deionized water 342, and/or a purge gas 344. The chemical component dosing pump 311 may be a rotary metering pump, a solenoid metering pump, a diaphragm pump, a syringe, a peristaltic pump, a piston pump, or other positive displacement volumetric device. The chemical component dosing pump 311 may used in conjunction with the volume measurement module 312 and/or the controller described herein as well as used singularly or coupled to a flow sensor. For example, in one embodiment, the chemical component dosing pump 311 includes a rotating and reciprocating ceramic piston that drives 0.32 ml per cycle of a predetermined chemical component. Alternatively, the dosing pump 311 may be replaced by a pressurized fluid delivery process or a vacuum delivery system, which draws chemical components into the module 312 by a vacuum source at port 317 or another port. The electrolyte source 304 may also be fluidly coupled to the module 312 by the dosing pump 311.
A first outlet port 330 of the volume measurement module 312 is generally coupled to the processing cells via valve or valve manifold 332 by an output line 340. Chemical components, such as at least one or more accelerators, levelers and/or suppressors, may be mixed or delivered for combining with an electrolyte flowing through a first delivery line 350 from the electrolyte source 304, to form the first or second plating solutions as desired. The purge port 317 is generally coupled to the module 312. The purge port 317 may be used to purge module 312 when necessary to recover from chemical component delivery errors that are detected by the volume measurement module 312.
While an embodiment volume measurement module is described herein for processing chemical components for electrolyte solutions, the invention contemplates that the volume measurement module may be used for processing additional liquids used in plating operations, including electrolytes, cleaning agents, such as water, etchants, or dissolving agents, among others.
While not shown, the invention also contemplates additional components using in fluid systems, including bypass valves, purge valves, flow controllers, or temperature controllers.
In another embodiment of the invention the fluid delivery system may be configured to provide a second completely different plating solution and associated chemical components. As such, multiple volume measurement modules may be disposed in the system to connect to one or more of the plating cells to provide the necessary plating solutions. For example, in this embodiment a different base electrolyte solution (similar to the solution contained in container 304 of
In order to implement the fluid delivery system capable of providing two separate chemistries from separate base electrolytes, a duplicate of the fluid delivery system illustrated in
The valve manifold 332 is typically configured to interface with a bank of valves 334. Each valve of the valve bank 334 may be selectively opened or closed to direct fluid from the valve manifold 332 to one of the process cells of the plating system 100. The valve manifold 332 and valve bank 334 may optionally be configured to support selective fluid delivery to additional number of process cells. In the embodiment depicted in
In some embodiments, it may be desirable to purge the volume measurement module 312, output line 340 and/or valve manifold 332. To facilitate such purging, the plating solution delivery system 111A, 111B is configured to supply at least one of a cleaning and/or purging fluid. In the embodiment depicted in
In an alternative embodiment of the system, a second delivery line 352 is tied between the first gas delivery line 350 and the dosing pump 311. A purge fluid of a purge liquid includes at least one of an electrolyte, deionized water or other suitable liquid from the respective sources, such as 304 and 342, may be diverted from the first delivery line 350 through the second gas delivery line 352, and through the dosing pump 311 to the volume measurement module 312. A purge fluid of a purge gas, such as nitrogen gas, from the respective sources 344 may be diverted from the first delivery line 350 through the second gas delivery line 352 and purge gas line 351 to the volume measurement module 312. The purge fluid is driven through the volume measurement module 312 and out the output line 340 to the valve manifold 332. The valve bank 334 typically directs the purge fluid out a drain port 388 to the reclamation system 232. The various other valves, regulators and other flow control devices have not been described and/or shown for the sake of brevity.
In one embodiment of the invention, chemical components for a first chemistry may be provided to promote feature filling of copper on a semiconductor substrate. The first chemistry may include between about 30 and about 65 g/l of copper, between about 35 and about 85 ppm of chlorine, between about 20 and about 40 g/l of acid, between about 4 and about 7.5 ml/L of accelerator, between about 1 and 5 ml/L of suppressor, and no leveler. The chemical components for the first chemistry is delivered from the valve manifold 332 to a first plating cell 150 to enable features disposed on the substrate to be substantially filled with metal. As the first chemistry generally does not completely fill the feature and has an inherently slow deposition rate, the first chemistry may be optimized to enhance the gap fill performance and the defect ratio of the deposited layer.
A second chemistry makeup with a different chemistry from the first chemistry may be provided to another plating cell on system 100 via valve manifold 332, wherein the second chemistry is configured to promote planar bulk deposition of copper on a substrate. The second chemistry may include between about 35 and about 60 g/l of copper, between about 60 and about 80 ppm of chlorine, between about 20 and about 40 g/l of acid, between about 4 and about 7.5 ml/L of accelerator, between about 1 and about 4 ml/L of suppressor, and between about 6 and about 10 ml/L of leveler, for example. The chemical components for the second chemistry is delivered from the valve manifold 332 to the second process cell to enable an efficient bulk metal deposition process to be performed over the metal deposited during the feature fill and planarization deposition step to fill the remaining portion of the feature. Since the second chemistry generally fills the upper portion of the features, the second chemistry may be optimized to enhance the planarization of the deposited material without substantially impacting substrate throughput. Thus, the two steps, different chemistry deposition process allows for both rapid deposition and good planarity of deposited films to be realized. The two chemistries may be provided sequentially from the same volume measurement module 312.
When utilized with a process cell requiring anolyte solutions such as the process cell 150 of
Upon starting the system with a fresh batch of electrolyte solution, the controller 115 waits until a set limit is reached in Amp-hours, such as 100, or maximum evaporation loss in the fluid delivery system 400, such as 2 L. If the evaporation loss is reached first, then the controller follows the process as illustrated by
Steps 505 and 606 are single dosing events. The additives and water are configured to provide one intermediate dose to the electrolyte solution to prolong the life of the electrolyte solution. Prolonging the life of the solution means providing enough fresh chemical components and water to the system to delay the need to dispose of the depleted solution and replace the solution with fresh solution. The volume of solution that is sent to the individual cells is approximately 15 L per bath. However, there can be a 0.5 L volume difference between the cell baths because of piping volume differences between the different cells. An individual, intermediate dose to the electrolyte solution is about 2 L. This volume is selected to provide at least 1 L of solution at the first and last of the solution addition to the individual cells. If the volume is too high, there is a risk of wasting fresh chemicals. If the volume is too low, there is a risk that the one dose of material will not prolong the life of the solution. Multiple doses at one time are also undesirable as they can lead to an overall solution increase that will alert the volume indicator on the vessel to shut down the system.
Multiple doses over a long period of time may also result in an overall volume increase in the system, specifically the volume in the vessel 410. If that volume is too high, the controller may stop the entire system. Also, the overall effectiveness of the system may decrease as the intermediate doses are based on an overall volume of solution that does not increase. Thus, occasionally, as the controller continues to provide intermediate doses to the system, a small volume of fluid may be removed from the vessel to prevent over-filling the vessel.
Marathon testing was performed to examine the effectiveness of this system. Over 700 amp-hours, one system exhibited acceptable accelerator, suppressor, and leveler when a dose was added every 100 amp-hours throughout the entire 700 amp-hours. Another system farther away from the main vessel had similar results, with slightly less variation in the concentration of the leveler. Over the course of the marathon testing, the constants for the algorithm to calculate the fresh dose components drifted less than 0.2 mL/amp-hour.
While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.
